310 YEirj'EF.IfAl'E ANIMALS. 



As i-ogardK the skeleton of the lUuiii hkiHh, it is not necessary to 

 add niueh to what was said in .sjieaking c^f the Vertehrata generally. 

 With few e.-cception.s, the spinal column is divisible into the same 

 regions as in man ^namely, the neck or cervical region, the back 

 or dorsal region, the loins or Inniliar region, the sacral region, and 

 the tail or caudal region fsee iig. 1 ")!)). In spite of the great differ- 

 ences observable in the lengtli cjf the neck in different Mammals, 

 the number of vertebi';e wliicli form the cervical region is extra 

 ordinarily constant, being almost invarialjly serun. In this res- 

 pect tlie Gii'atfe, Avhich is the longest-necked of ilammals, agrees 

 witli the Whale, whicli e.-in hardly be said to have a neck at all. 

 The vertebra' of tlie back or dorsal rei;io]i are mostly thirteen in 

 nundier, but are often more, lii man there are only twelve; a)id 

 in some cases tliere are cinly ele\'en or ten. The hnnbar vertebra^ 

 are usually si.K or seven in number ; live in Man ; rarely less than 

 four. The sacral vertebr;e are irsu.ally amalgamated to form a 

 single bone — the xnrni/ii — Ijut this is wanting in the Whales. T)ie 

 number of vertebne in the t;ul or caudal region varies from four 

 to as many as iive-andfoity, .-11111 they are usually' freely movable 

 nj)on one another. The tlior.-icic cavity or chest in ^Mammals is 

 /ihvays enclosed by a seiies of libs ; the number of wliich varies 

 with the nundjer of the dorsal vertebra'. As a rule, the ribs are 

 united to the breast djone or sternum in front, not by bony jjieces, 

 as in birds, but by cartil.-iges. ( hily the front ribs reach the ster- 

 num, and tliese are calleil the "true" ribs; the hinder ribs fall 

 short of the breast-bone, .-md are called the "false" I'ibs. The .ster- 

 mnn is coni|iosed of sevei'al jiieces, jil.-iced one behind the other, but 

 usually am,'ili;amated to fiu'm a single bone. It is usually long and 

 narrow in sliajie, ami is iinly rarely furnished with an}^ ridge or 

 keel, as it is in llirds. The i-egular number of limbs in the Mam- 

 mals is four, two anterior and two posterior; and for this I'eason 

 tlie Mammals are often s|)cikeii of as (^>uadru|ieds. Some Mammals, 

 however, such as the Whales and Dolphins, have only the anterior 

 limlis, and many of the Amphibia and Keiitiles walk U]ion four legs. 

 As reg.-irds the structure of the fore-limbs (Iig. KiO), the general 

 conformation of the limb has lieeii jirevimisly iioteil. The slioulder- 

 blade or xra/uilu is never w;inting, and is generallv broad and Hat. 

 The coracoid bones, which form such a marked feature in the pec- 

 toral arch of the TSirds, are incomplete, and are fused with the 

 scapula', of which they form the so-ealled "coracoid process." In 

 the Monotrematous Mammals alone are the cor.-icoids distinct bones, 

 sniiii'ieiilly develo|ied to articulate with the sternum. The coll.-ir- 

 l>oiies oi- clavicles are often rudimentary or absent, and, when pres- 

 ent, are iicM/r united into a single bone. The humerus ]:resent3 



